1. Field of the Invention
This invention relates to marking significant events in a seismic trace. More particularly, it relates to a computer system for automatically detecting significant events in a seismic trace.
2. Description of the Prior Art
The prior art has worked with two different approaches (1) solving for the position of horizons and (2) determining the location of significant changes by amplitude zero-crossings in seismic traces.
Attempts to solve for the position of horizons in the general and practical case have not been successful. In principle, if the seismic source is known exactly and if the earth does not attenuate the seismic signal, the seismic data could be deconvolved to obtain the locations of horizons. However, the source can only be known approximately and, more importantly, the earth attenuates high frequencies in the signal, severely reducing the resolution of seismic data. As a result, any single significant change in a seismic trace is likely to correspond to not just one, but many confused reflections which cannot be distinguished.
Previous approaches that have determined significant changes by amplitude zero-crossings in seismic traces essentially amount to an assertion that the significant changes of interest are primarily determined by points where the trace changes sign. However, this approach is not suitable for mapping seismic events whose amplitudes change sign without a zero-crossing.
The invention of this specification distinctly marks significant changes (turnings) such as local extrema, saddle points, inflections and other high-order changes.